Aluminum casting with a bronze insert



June 16, 1959 H. BENHAM ALUMINUM CASTING WITH A BRONZE INSERT Filed May 24. 1956 ATTORNEY provide a long-wea1ing bronze-insert United Sttes Patent CASTING WITH A BRONZE. INSERT T Harold LQBenham, Bedford, 'Ind., assignor to General Motors Corporation, *Detioit, Mich, a corporation of Delaware ApplicationMay 24, 1956, serial No. 537,152

invention relates to a method of forming an aluor aluminum alloy casting having a copper base 19-56, respectively, in the name of Earl J. Clark. 1 The aluminum alloy bearing in this form of journalbearing assembly functions as a thrust hearing as well as a sleeve hearing. In some modifications of this assembly the thrust bearing surface provided by the aluminum alloy is entirely satisfactory because of excellent. lubrication, while in others this surface wears at an excessive rate. Under the latter circumstances it is desirable to in the end of the aluminum alloy bearing sleeve.

However, in manufacturing this hearing, if the aluminum base alloy is cast directly against the bronze insert, one or more low-melting point. alloys are formed with an attendant reduction in the volume of the two metals. It was found, for example, that when the molten aluminum contacts the bronze, zinc and/ or various other constituents in the bronze diffuse into the aluminum and form a eutectic mixture such as aluminum-zinc. The

lower melting point constituents in the bronze actually emigrate to and alloy with the aluminum base metal.

These constituents, such as lead, zinc, etc., are frequently essential to provide the bronze insertwith desirable hearing properties, and if they alloy with the aluminum the effectiveness of the insert is substantially reduced.

It is believed that the copper in thebronze and the aluminum also form a relatively low melting point alloy. This absorption or diffusion into the aluminum of the copper or other constituents in the bronze produces shrink cavities inthe aluminum alloy at. the interface. of the insert and the aluminum alloy. These shrink cavities or worm holes. are formed because the aluminum solidifies against the insert before the aforementioned diffusion is complete, thus entrapping the lower melting point ,the formation of this and other undesirable low-melting p-Qinteutectics in the bearing.

Accordingly, a principal object of the present invention is to provide a method of casting aluminum. or aluminum alloy into contact with a copper base alloy so that there is no migration or diffusion of the constituents in the copper base alloy into the aluminum. A further object of this invention is to provide a process for casting aluminum or an aluminum alloy against a bronze insert in a manner which prevents the aforementioned de-zincification. of bronze or formation of other undesirable lowmelting eutectics. A still further object of the invention is to provide a thrust bearing produced by casting aluminum around a. bronze insert in such a manner that alloying of the two metals is substantially eliminated and in which the insert is mechanically locked in position in the aluminum casting.

These and other objects are attained in accordance with the present invention by the used a copper oxide barrier layer between the. bronze insert and the aluminum alloy. Specifically, a black copper oxide coating is formed on the surfaces of the bronze by heating the insert to the red-hot temperature range before casting the aluminum around it. As a result, practically no alloying occurs between the bronze and the aluminum base alloy, yet a: mechanical bond retains the two metals in close surface contact.

Other objects and advantages of this invention will more fully appear from the following detailed description thereof, reference being made to the accompanying drawing in which:

Figure 1 is a longitudinal sectional view of a portion of a journal-bearing assembly embodying the present invention;

Figure 2 is a longitudinal sectional view of a portion of a modification of the journal-bearing assembly shown in Figure 1; and

Figure 3- is an enlarged sectional view of the ring-shaped bronze insert shown in Figures 1 and 2.

Referring more particularly to the drawing, in Figure l is shown part of a sealed-cartridge. journal-bearing assembly for railway freight and passenger cars. An axle 10. having a journal portion. 12 is shown rotatably supported within an aluminum alloy sleeve bearing 14. If desired, the bearing surface of this. sleeve may be provided with a thin overlay 15 of a suitable lead base alloy, such as lead-tin or lead-indium. A housing 16 surrounds the. journal-bearing assembly and is provided with a portion 18 at its inner end forming a support for an annular oil. seal 20.

As shown in Figure l, the outer periphery of the oil seal contacts the, housing and the inner periphery contacts a hardened thrust ring 22 secured to the axle by a shrink fit. This thrust ring is shaped so as to have portions 24 and- 26 contacting the journal and to leave a space 28 between the thrust ring and a portion of the journal. The thrust ring may be formed of suitable hard wear-resistant material such as carbonitrided and hardened steel. Adjacent the thrust ring and bronze insert there is provided an annular groove 29 in the housing to permit return of excess oil to an oil reservoir, not shown, in the lower portion of the housing.

The. axle journal 12 is provided with a seamless hardened journal sleeve 30 which is shrink fitted around the journal or attached thereto by other appropriate means. This. journal sleeve may bemade of any suitable wearresistant metal, such as steel having its outer surface carbonitridedand hardened. During operation this sleeve is, in effect, a portion of the rotating, journal, but it may be readily replaced should excessive wear or scoring occur.

The end face 32 of the thrust ring 22 is normally spaced at 34 from the end of the sleeve bearing 14 as illustrated in Figure 1. However, when the. railway car is traveling around a curve or otherwise when there are a plurality of circumferentially spaced openings 42.

forming the bearing sleeve 14 the aluminum alloy is cast against this annular insert so that the molten aluminum 1 alloy flows into the openings 42 to form locking fingers 'forcescausing relative axial movement between the journal and hearing, this space 34 will close and the adjacent end of the bearing sleevewill contact the end face of the thrust ring. Underthese circumstances, excessive wear of the end of the aluminum alloy bearing sleeve mayoccur, particularly if not thoroughly lubricated, un-

'- less it is provided with a more wear-resistant surface.

Accordingly, a bronze insert 38 is located at the flanged end 40 of the bearing sleeve.

This bronze insert is ring shaped and is provided with In 46 which rigidly hold the insert in position against the flanged end 40 of the bearing sleeve casting. Either during the casting process or by subsequent machining it is preferable to form the *fingers 46 so that they are slightly recessed axially and do not contact the end face 32 of the thrust ring 22. In this manner the bronze insert is the only portion of the bearing which functions as a thrust surface. It will also be noted that the openings 42 in the bronze insert ring 38 are tapered at 44 so that the aluminum locking portions 46 are flared radially 'outward at their outer ends 48 to prevent axial movement of the insert relative to the aluminum bearing sleeve.

In the modification of the invention shown in Figure 2 at the thrust bearing end of "the aluminum alloy sleeve 30. Otherwise this end of the sleeve would be subject to rapid wear and galling due to inadequate lubrication and the thrust ring 22 and the bearing sleeve. Even when the thrust bearing surface is very poorly lubricated, the bronze insert will not gall.

The annular bronze insert 38 may be formed of any securely retain the ring against the surfaces of the casting.

Among the aluminum base alloys which may be used to form the bearing sleeve 14, excellent results have been obtained with the alloy described in United States Letters Patent No. 2,238,399 in the same of Alfred W.

Schluchter. Hence an aluminum base bearing alloy consisting essentially of 0.05% to 5% cadmium, 0.3% to 11% silicon and the balance aluminum is satisfactory. A somewhat harder and stronger aluminum alloy bearing "which may be employed is described and claimed-incopending patent application Serial No. 250,191, filed on October 6, 1951, now Patent No 2,766,116, October 9, 1956, in the name of Alfred W. Schluchter. Thusthe aforementioned aluminum base alloy may be further improved for some applications by the presence of 0.05% to the oil seal is omitted. With this arrangement'it is par- I ticularly desirable to employ the annular bronze insert 38 magnesium and/or 0.1% to 2.25% chromium. "In all instances, however, it is desirable to use 'analloy containing at least 80% aluminum. p

' Q Not only does the CuO film function as a barrier to prevent the low-melting metal constituents in the bronze 3O from alloying with the molten aluminum, but ital'so the presence of foreign particles in the space 34 between ,7

affords several other advantages. The hot copper oxide coating permits the aluminum alloy to closely contact the bronze insert 'on cooling. Moreover, since the molten aluminum alloy may be poured around the bronze insert while the latter is still hot, blows will not-be procopper base alloy suitable for thrust bearing applications. various alloys containing at least 50% copper and minor amounts of other metals. Among the alloying constituents which may be used are tin, zinc, nickel, lead, man- "g anese, aluminum, silicon, arsenic, antimony and phos fphorus.

Normally the bronze should not contain more than about 20% tin or 30% zinc. Since nickel is completely miscible in copper, it also may be present in appreciable amounts but preferably not in excess of approxi- Qmately 20%. j 1% to 5% silicon and not in excess of 1% phosphorus. Usually the'manganese and lead contents of the bronze Such a bronze usually will contain about should not exceed approximately 5% and 3%, respectively. A preferred bronze composition for use in the above-described thrust bearing application is one con- I-Ience the term bronze is intended to include 1 duced in the'aluminum alloy nor will it be chilled during the casting operation. i

As a result of the above-described process, the-bronze insert is mechanically locked in place, andno metallic bonding occurs between it and the aluminum casting." It is ;believed that the bronze and aluminum alloy do not 'actually'touch and that the only contact is between the CuO barrier layer and the aluminum alloy. For all practical purposes the CuO is insoluble in the aluminum alloy because of the short contact time between the molten aluminum and the bronze and the relatively low casting temperature of the aluminum alloy. While this invention has been described by means of certain specific examples, it will be understood that the scope of the invention is not to be limited thereby exsisting essentially of 10% zinc, 0.05% lead, 0.05% iron and the balance substantially all copper.

After the openings 42 have been drilled or otherwise formed in the bronze insert 38 the surfaces of the insert are provided with a copper oxide barrierlayer 50 which cept as defined in the following claims. Iclairn: H

1. A bearing comprising an aluminum alloy-casting and a copper base alloy member forming a bearing surface secured to said casting, the surface of said copper prevents the aforementioned undesirable alloying of the bronze with the aluminum. Such a barrier layer precludes metal constituents in the bronze from alloying with the molten aluminum atthe interface of the two metals during casting of the aluminum alloy. The copper oxide -A temperature between 1200 F. and 1400" F. is preferably employed. This heating, which brings the temperature of the bronze insert into the red-hot range, provides the insertwith a coating or film of black copper oxide due to the oxidation of the copper in the bronze.

The black copper oxide barrier layer provided is extremely thin, generally not in excess of approximately 0.001 inch in thickness. This copper'oxide is the mono 'oxide, 010, which is produced by the rapid oxidation due to the flame treatment. 7

base alloy member adjacent said casting beingpi'ovided with a thin barrier layer of CuO. 2. A' bearing comprising an aluminum alloy casting and a copper base alloy insert forming a thrust bearing surface, said insert being mechanically'secured to said layer may be formed by heating thebronze insert to a temperature of 1000 F. to 1400" F. over an openflame.

f casting,.the surface of said insert adjacent said casting being provided with a barrier layer of copper oxide having a thickness not in excess of approximately 0.001 inch.

' 3. A bearing comprising a cast aluminum base-alloy sleeve member and a zinc-containing copper basen alloy Tthrust bearing member of generally annular shape secured to the end of said sleeve member, the surfaces of said thrust bearing member contacting said sleeve member being provided with a surface layer of CuO having a thickness not in excess of approximately 0.001 inch.

' 4. A bearing for use in railway journal-bearing'assemblies and the like, said bearing comprising a cast aluminum base alloy sleeve member and a generally an- "nular bronze insert secured to an end of said sleeve '75 -member and forming a thrust .bearing surface, said insert being provided with an opening in a surface adjacent said sleeve member, said sleeve member having a portion extending into said opening to mechanically lock said insert against said sleeve member, said insert being provided with a thin surface layer of CuO.

5. A bearing comprising a cast aluminum base alloy sleeve having bearing surfaces thereof coated with a thin overlay of a metal selected from the group consisting of lead-tin alloys and lead-indium alloys, and a generally annular bronze insert secured to an end of said sleeve and forming a thrust bearing surface, said insert being provided with a plurality of openings in a surface adjacent said sleeve, said sleeve having portions extending into said openings to mechanically lock said insert against said sleeve, surfaces of said insert adjacent said sleeve being coated with a thin layer of OuO.

6. A composite article comprising a bronze member having outer surfaces provided with a thin layer of C110 of a type produced by heating said surfaces in an open flame to a temperature of approximately 1000 F. to

1400 F., and a cast aluminum base alloy member contacting said CuO coating and having a portion mechanically locking said bronze member to said aluminum base alloy member.

7. A composite article comprising a bronze member having outer surfaces provided with a thin layer of CuO, said bronze member being provided with a plurality of openings therein, and an aluminum base alloy casting abutting said C layer having portions extending through said openings to retain said bronze member in abutment with adjacent surfaces of said cast-ing.

References Cited in the file of this patent UNITED STATES PATENTS 2,555,497 McCullough et a1. June 5, 1951 2,582,433 Hitchcock Ian. 15, 1952 2,590,761 Edgar Mar. 25, 1952 2,649,651 Townhill Aug. 25, 1953 

1. A BEARING COMPRISING AN ALUMINUM ALLOY CASTING AND A COPPER BASE ALLOY MEMBER FORMING A BEARING SURFACE SECURED TO SAID CASTING, THE SURFACE OF SAID COPPER BASE ALLOY MEMBER ADJACENT SAID CASTING BEING PROVIDED WITH A THIN BARRIER LAYER OF CUO. 